Electrical power distribution systems for industrial and residential power users a range of equipment that incorporate one or more moving parts, the majority of which equipment is installed outdoors. Such equipment include for example circuit breakers, earthing switches, overload protectors. A circuit breakers is an example of a distribution device with one or more moving parts. Circuit breakers of different types are used to control and adjust the distribution power, switching power feeds on and off and switching from or to different lines or feeders as required. A circuit breaker must be able to break and make normal current loads and above all, be able to interrupt short-circuits due to faults in the system. Modern circuit breakers have interrupting times of around 20 milliseconds and may break a circuit automatically in response to a signal from a fault sensing relay in the power distribution system. By breaking or making a circuit on command from a remote control location, automatically operated circuit breakers provide a significant improvement over manually operated circuit breakers.
Circuit breakers are the most important active components in an electrical power distribution system. Maintenance has to be carried out on circuit breakers to ensure that they operate as designed when required. Moving parts of equipment installed outdoors are subject to many factors that can cause wear, damage or failure, factors including weather conditions, corrosion, lightning strike, animal intrusions etc. However, the costs to the utility owner of preventive maintenance and of scheduled maintenance are high. On the other hand, when a circuit breaker fails the costs or penalties arising from an otherwise avoidable temporary blackout, brownout or other power interruption may be extremely high when a large number of industrial and/or residential consumers are involved.
However, it is not only a question of economic costs to the utility. Making unnecessary repairs may increase the risk of fault at the distribution installation.
U.S. Pat. No. 6,466,023 entitled: Method of determining contact wear in a trip unit, describes a method of determining contact wear in a trip unit of a circuit breaker. The trip unit includes a processor and memory and an algorithm stored in a memory of the trip unit calculates cumulative energy dissipated in the breaker contacts using the current signal detected at the time of separation. Measurement of cumulative energy dissipated in the breaker contacts is said to be proportional to contact wear. Maintenance setpoints are then determined based on industry standard tests and thresholds are provided within the algorithm for notifying local or remote personnel of a necessary maintenance procedure. According to the disclosure, a condition of a trip unit of a circuit breaker requiring maintenance attention may be signaled. However, the estimated condition of the contact points of a circuit breaker is only an estimate and is also only one of many parameters relevant to a condition of a circuit breaker.
WO0193399 A entitled: Browser-enabled remote user interface and automated expansion analyzer for telecommunications power systems; describes an interface for a control unit, and a control unit, for a telecommunications power system. The control unit may be operated by engineers from a remote location to control and/or switch power supplies using such control units, via a browser-enabled interface. Each control unit has bus connections to rectifier units in a telecommunications power supply system may supply state information. However, the control unit described is dedicated to the requirements of a telecommunications power supply system, typically including battery-based back-up power supplies, wherein the equipment is usually arranged indoors, and where the technical problem is one of switching from one power supply to another.
The technical requirement for maintenance of electrical distribution devices with moving parts, such as circuit breakers, in a power distribution system due to such events as lightning strikes or mechanical failure of equipment installed out of doors, and/or taken together with the amount of use, number of operation events etc. The device performs is not addressed in the prior art. Neither is the problem of maintaining such devices as circuit breakers in a timely fashion described.